1. Field of the Invention
The present invention relates to a liquid crystal display consisting of two carrier plates which enclose a liquid crystal layer between them and its manufacture. More particularly, the invention relates to a layer at least one of the carrier plates which orients the liquid crystal layer which is manufactured using an ultrasonic, stationary wave field to introduce parallel grooves into the surface of the orientation layer.
2. Description of the Prior Art
Among the multitude of alignment processes known and tested up to now, the so-called oblique sputtering method, (See Applied Physics Letters, 21:173 (1972)), has traditionally been employed. Advantageously, obliquely sputtered layers orient uniformly well and reliably, and moreover, do not attach the liquid crystal substance. However, oblique sputtering still has a significant fabrication cost, especially when the liquid crystal molecules are to assume a small angle of incidence, (a maximum of approximately 5.degree.), with respect to the substrate plane. This slight tilting which is strived for in many areas of employment requires a refinement of the sputtering technique. One method, for example, applies two layers of different thickness and with different angles to the substrate, (Physics Letters 29:691 (1976)). In addition, there is a further disadvantage with sputtering. Upon sputtering from oblique directions, elevations located on the substrate such as electrode segments or spacers cast shadows in which the liquid crystal is not oriented or is only imperfectly oriented. These shadow effects can be eliminated when one profiles the orientation layer by means of a friction technique. Such a mechanical treatment has the further advantage that the liquid crystal molecules are somewhat inclined with respect to the substrate surface in and of themselves. However, rubbed layers, even when they are processed by machine, still only deliver conditionally acceptable liquid crystal textures.
Such an orientation technique in which the groove or channel system is generated by means of the exposure of a light-sensitive layer with interfering coherent light sources is described in the German OS No. 2,256,317. Films which are structural using this interference pattern possess faultless orientation. However, this special photo-technology requires a number of fabricating steps and is less suited for mass production.